Recently, Light-emitting diodes (LEDs) are widely used in many applications such as optical communication systems, displays and light illuminating components. Most of these applications require LEDs with high power, high luminance and high efficiency. However, it is expected that by expanding the active device area with small adjustments in existing chip designs is insufficient to meet high power and high brightness requirements. An alternate approach for device grown on sapphire substrates is to employ the flip-chip configuration in which the device is flip-chip mounted on a thermal-conductive sub-mount and the light is collected through the sapphire rather than a semitransparent current spreading layer on top of p-GaN. ²...[ Read more ]

Recently, Light-emitting diodes (LEDs) are widely used in many applications such as optical communication systems, displays and light illuminating components. Most of these applications require LEDs with high power, high luminance and high efficiency. However, it is expected that by expanding the active device area with small adjustments in existing chip designs is insufficient to meet high power and high brightness requirements. An alternate approach for device grown on sapphire substrates is to employ the flip-chip configuration in which the device is flip-chip mounted on a thermal-conductive sub-mount and the light is collected through the sapphire rather than a semitransparent current spreading layer on top of p-GaN.

In this research project, high power 1 x 1mm² InGaN-GaN multiple quantum-well (MQW) LEDs were fabricated and flip-chip packaged on silicon (Si) sub-mounts. The characteristics were evaluated by current-voltage (I-V), as well as optical power (L-I ) measurements. Experimental results show that the flip-chip LED exhibited a higher output power than that of conventional top-emitting LED and with comparable operation voltage at the same injection current density. The output power of the 1 x 1mm² flip-chip LEDs at injection current of 600mA is 57mW. At the injection current density from 220 to 600mA/mm², the wall-plug efficiency of 1 x 1 mm² flip-chip LED is 1.7 times higher than that of conventional top-emitting LED.